(CNN) -- Venezuelan authorities have detained the captain of a U.S.-flagged ship docked in a northwestern port city, accusing him of arms trafficking, according to crew members on board.
An official at the U.S. Embassy in Venezuela said the captain and 15 crew members on board the ship had been held in Maracaibo, Venezuela, and that U.S. authorities were trying to find out additional information from Venezuelan officials.
Earlier Thursday, a U.S. State Department official who asked to remain anonymous said the department was "looking into the status of the captain and crew of the U.S. vessel, Ocean Atlas, currently anchored in Maracaibo."
"We are in contact with the government of Venezuela on the matter, and are working to provide all appropriate consular assistance at the earliest opportunity," the official said.
Venezuelan officials did not immediately respond to requests for comment.
A crew member on the ship who asked to remain anonymous because of security concerns said the ship had been detained for nine days and the captain had been taken from the ship Wednesday night.
The crew member said in an e-mail Thursday evening that arrest warrants had been issued for the entire crew, who would have to give depositions on Friday morning.
"We will be taken two people at a time for questioning and then brought back," he said, adding that a U.S. consular representative had visited the crew and said he would accompany them.
The crew member gave a detailed account of what had happened to the ship since it docked in Maracaibo on August 29.
A few hours after the ship arrived, it was boarded by officials from Interpol, Venezuelan police officers and narcotics investigators who said they had received a tip that the vessel was smuggling drugs, the crew member said.
A search of the ship and cargo turned up no drugs, he said, but the officials did find weapons the ship's security team keeps in a locker for when the vessel goes through areas where piracy is a threat, like the Gulf of Aden.
The captain had declared the weapons upon arrival in Maracaibo and received clearance, according to the crew member, but the Venezuelan authorities now said the ship didn't have permission to have them on board and confiscated them.
On Saturday, the crew was told the ship was under investigation for arms trafficking, he said, and on Wednesday morning the captain said the ship had been officially charged.
On Wednesday night, after the captain made a court appearance during the day, 20 to 30 armed soldiers demanded to be let on board, the crew member said.
They held the crew at gunpoint before sending them to the mess, he said. They then met with the captain in his office and took him away.
The captain hasn't returned to the ship since, the crew member said, but he has talked on the phone to the chief mate.
The sister of another crew member, who has been in regular contact with her brother and asked not to be identified for security reasons, said crew members held aboard the ship have heard that the captain has been charged with arms trafficking. The captain was detained after he refused to let authorities arrest the crew, she said.
The Ocean Atlas, built in 2000, is a 393-foot-long multipurpose vessel that has two electro-hydraulic cranes and a grain and bale capacity of 395,000 cubic feet, according the website of Intermarine, a managing agent of vessel operating companies.
CNN's Elise Labott, Marilia Brocchetto and Arthur Brice and journalist Osmary Hernandez contributed to this report.