PIEDRAS NEGRAS, Mexico (AP) _ The opposition National Action Party sent delegations to the state capital of Saltillo and Mexico City on Thursday to seek information on five party supporters who have been missing since a violent protest last weekend.

Ramon Aguilera, a spokesman for the party, said in a telephone interview that the party holds state judicial police responsible for the disappearance of the five.

''Nothing is known about them still. No one knows anything. They're hiding everything from us,'' Aguilera said.

The government has not commented on the opposition claims, but Aguilera said local party delegations had gone to Saltillo, capital of Coahuila state, and Mexico City looking for information.

Violence flared in Piedras Negras after Carlos Juaristi Septien of the dominant Institutional Revolutionary Party was sworn in Saturday as mayor.

The National Action Party claims the election was rigged, and that its candidate, Eleazar Cobos, was the actual winner.

The state electoral commission, which is controlled by the Institutional Revolutionary Party, declared the dominant party the winner in 35 of 38 municipal elections held Dec. 2 in Coahuila state.

Meanwhile, the army, which was called out in at least four Coahuila cities because of the election protests, remained on patrol in Piedras Negras on Thursday.

Juaristi Septien started work Wednesday in temporary offices set up in a hotel owned by his family. The municipal complex was damaged in a fire set during the protests. At least one man died and nearly 80 people were injured in Piedras Negras.

National Action Party supporters continued to occupy the municipal building in Monclova, 155 miles to the south, where another Institutional Revolutionary Party candidate was declared the winner.