CIUDAD JUAREZ, Mexico (AP) _ Authorities in this border city have formed a quick-response unit to deal with a rash of bomb threats that followed a rebel uprising in southern Mexico.

The 50-person unit includes firefighters and police officers who will search for explosives and investigate their origins, said municipal police Capt. Rafael Falcon.

About 20 bomb threats were received this week in Ciudad Juarez government buildings, schools and businesses, said Fire Chief Miguel Garcia.

All the threats have been false, but at least one of the callers identified himself as a member of the Zapatista National Liberation Army. The rebel group was behind an uprising in Chiapas state in southern Mexico.

Federal officials have downplayed the threat in Ciudad Juarez, across the border from El Paso, Texas. They say the calls are coming from isolated opportunists.