Authorities searched overnight for six federal inmates who escaped a South Texas jail by overpowering a guard and cutting through at least four fences, officials said.

Hidalgo County Sheriff Lupe Trevino said the six men escaped at about 11:30 p.m. CDT Tuesday from the East Hidalgo Detention Center, a privately operated jail in La Villa, about 20 miles north of the Mexican border.

The Sheriff's Office was leading a search involving more than 60 officers, including local officers as well federal agents from the Border Patrol andU.S. Marshals Service, Trevino said. Helicopters and bloodhounds were being used in the search.

"We're considering all six individuals very dangerous and armed," Trevino said.

He said the search was focused on an approximately 4-square-mile area.

Trevino said he didn't know whether the prison guard who was overpowered by the escapees suffered any injuries.

Trevino said one of the escapees was an American being held on drug charges. He said the five others were Mexican nationals thought to be members of a criminal gang known as "Raza Unida."