(CNN) -- The director of public security in the border city of Nuevo Laredo, Mexico, was gunned down Wednesday night, officials said, though details of the incident remained scarce.
Gen. Manuel Farfan Carreola, who served as police chief, was shot near his office by unknown assailants, said Everardo Sanchez, a spokesman for Mexico's attorney general's office. He had been in the position since a new administration assumed city leadership on January 1.
Rumors of how many others were killed along with the police chief swirled in Nuevo Laredo Thursday, but city officials declined to go on the record with details surrounding the incident. The state government, which is leading the investigation, was expected to hold a news conference Thursday evening.
"Obviously, the news about his death is out, but the circumstances have been in the shadows," said Joe Baeza, a spokesman for the Laredo, Texas, Police Department. The Laredo Police Department keeps in touch with its cross-border colleagues.
The investigation is an ongoing process, Baeza said, though early reports that have reached his department were that five of Farfan's security team were killed in the shooting.
The Laredo Police Department received several reports of sporadic gunfire on the Mexican side of the border, possibly related to the fallout of the killing, Baeza said.
"There's reported instability on the Mexican side," he said.
Nuevo Laredo is one of the battlegrounds that is being contested by rival drug cartels. The Gulf cartel and its former enforcers, Los Zetas, have been fighting over the territory and its lucrative smuggling routes. The Sinaloa cartel also has been fighting for years to get a foothold in the area.
CNN's Nick Valencia contributed to this report.