As tensions eased at a prison near the Texas border taken over by inmates in a weekend riot, a U.S. diplomat predicted Mexican authorities would rely on negotiations and not storm the facility.

Some prisoners surrendered weapons on Sunday and relatives brought food and water to the Tamaulipas prison, where 18 inmates were killed and eight wounded in rioting triggered by the shooting of a reputed drug lord incarcerated there.An estimated 100 police officers and troops stood guard Sunday outside the prison, which is in a residential neighborhood in western Matamoros.

Police said some prisoners were armed with automatic weapons.

Donald E. Wells, the U.S. consul in the border town, said Sunday evening that Mexican authorities weren't likely to storm the jail, as some officials had earlier predicted.

"They have never done that historically. They usually negotiate their way back inside and they do not move back in with a show of force," he said.

The diplomat said that already "a state of calm" had returned inside the facility.

"We know that the governor's chief of staff has been in the prison talking to the prisoners, so that we are fairly sure that there is not a dangerous ongoing situation to the prisoners," Wells said.

He said some prisoners surrendered their weapons on Sunday.

Overcrowding was a major factor in the escalating tension at the prison, which was built for 250 but housed about 1,500, Wells said, adding that the overcrowding resulted from President Carlos Salinas de Gortari's crackdown on the drug trade.

Mexican prisons are not as heavily guarded as American prisons and authorities rely on trustees to maintain order, a system that often leads to inmate abuses.

Thirty-two inmates at the prison have identified themselves as Americans, including two women, and Wells said none of them was among the dead or wounded.

Earlier Sunday, relatives of the inmates were allowed to drop off food and water. Later, they entered in groups of five to see the prisoners.

Authorities said the trouble began Friday evening after a prisoner tried to shoot reputed drug lord Oliverio Chavez Araujo.