Washington (CNN) -- The acting inspector general of the Department of Homeland Security is investigating the Secret Service prostitution scandal in Colombia, in addition to four congressional committees as well as internal reviews by the agency, the military and the White House.
The top legislators on the Senate Homeland Security and Governmental Affairs Committee said Tuesday they sent a letter to Secret Service Director Mark Sullivan asking for information on the incident last month in Cartagena, Colombia, that has resulted in nine agents resigning or in the process of being forced out.
Three other Secret Service agents were cleared of serious misconduct, and the military is investigating the alleged involvement of 12 service members.
On Monday, the Homeland Security official announced his separate investigation of the incident, which embarrassed the government and raised questions of a possible security breach before President Barack Obama arrived for the Summit of the Americas.
The "field work is beginning immediately," acting Inspector General Charles Edwards said in a statement.
Meanwhile, Sullivan faced a pair of deadlines Tuesday to answer dozens of questions about the issue.
House Homeland Security Committee Chairman Peter King, R-New York, submitted 50 questions to Sullivan, while House Oversight Committee Chairman Darrell Issa and Rep. Elijah Cummings, the panel's ranking Democrat, have 10 questions they wanted answered, including a precise time line of exactly what happened in Cartagena.
"The incident in Cartagena is troubling because Secret Service agents and officers made a range of bad decisions," said a letter from Issa, R-California, and Cummings of Maryland.
The pair also sent a letter to Defense Secretary Leon Panetta requesting details of the military investigation by May 8.
In their correspondence to Panetta, Issa and Cummings said security personnel showed an "alarming lack" of "character" and "judgment."
The Senate Judiciary Committee questioned Homeland Security Secretary Janet Napolitano about the controversy at a hearing last week. On Tuesday, Sen. Joe Lieberman, an independent from Connecticut who chairs the Senate Homeland Security Committee, and ranking Republican Sen. Susan Collins said they sent Sullivan a letter Monday that also sought answers about what happened.
"We wish to determine whether those events were indicative of a pattern of behavior by agents or officers of the Secret Service, and need to be addressed systemically, or if they instead constituted an isolated incident warranting action only with respect to the individuals involved," said the letter from Lieberman and Collins.
The U.S. Southern Command expects to finish questioning the 12 military personnel implicated in possible wrongdoing this week before forwarding its findings to military lawyers for review, and then to Gen. Douglas Fraser, commanding general of the U.S. Southern Command, a Defense Department official said Monday.
Last week, the Secret Service distributed new rules for its agents on assignment intended to prevent a repeat of such alleged misconduct, according to two government sources familiar with the resulting investigation.
Called Enhanced Standards of Conduct, the new guidelines given to all Secret Service personnel make clear that standards of behavior required in the United States apply on missions abroad, the sources said.
Effective immediately, the new standards require detailed briefings before each trip that will include safety precautions and any necessary designations of establishments and areas that are "off limits" for Secret Service personnel, the sources said.
Also in the new standards, foreigners are banned from Secret Service hotel rooms at all times, except for hotel staff and host nation law enforcement and government officials on official business, according to the officials, and all Secret Service personnel are prohibited from going to a "nonreputable establishment."
The new standards specify that U.S. laws apply to Secret Service personnel when traveling, rendering invalid the excuse that specific activity is legal in the foreign country, the officials said.
In addition, the new guidelines allow moderate alcohol consumption when off duty, but prohibit alcohol consumption within 10 hours of reporting for duty or at any time when at the hotel where the protected official is staying, the officials explained.
An additional supervisor from the Office of Professional Responsibility will now accompany the "jump teams" that bring vehicles for motorcades and other transportation, the officials said. Agents involved in the Colombia incident were part of such a jump team.
Allegations of further transgressions by agents have emerged after the initial reports of heavy drinking and consorting with prostitutes last month before Obama arrived in Cartagena.
Recent claims include an account from El Salvador described by CNN affiliate Seatte TV station KIRO as very similar to the Colombia scandal, involving members of the Secret Service and other government agencies.
However, Panetta said last week that his department is not investigating any of its troops over the reported incident in El Salvador, while State Department spokesman Victoria Nuland said embassy staff in El Salvador were being questioned about the allegations
The Drug Enforcement Administration also is prepared to look into, "in an appropriate manner and immediately," allegations that it deems "credible" regarding its agents in El Salvador, agency spokesman Rusty Payne said. But he added that, while the DEA had seen news reports, "we are unaware of any allegations of misconduct."
CNN's Ed Payne, Ted Barrett, John King and Dana Bash contributed to this report.