MONCLOVA, Mexico (AP) _ A defeated mayoral candidate party and his supporters staged a sit-in at City Hall on Tuesday to press their claims of vote fraud. Officials took no action to oust the protesters.

Armando Cortes Guerrero, duty officer at the Monclova federal police post, said about 100 National Action Party supporters were gathered in the plaza in front of City Hall. He said no violence was reported in connection with the protests.

Cortes Guerrero said Pedro Pascual Esquivel, the opposition party candidate in the Dec. 2 election, was inside the building with some supporters and was refusing to turn the building over to Salvador Martinez, the declared winner of the mayoral race.

Martinez is a member of the Institutional Revolutionary Party, which has controlled the presidency and state governments for more than 50 years.

Esquivel and his supporters spent Monday night inside City Hall. Other supporters stayed in the plaza to prevent Martinez from entering.

The two men both were sworn in Monday as mayor of this northern city in rival ceremonies - one conducted by the outgoing mayor, also a member of the opposition party, and the other by a representative of the state government, controlled by the Institutional Revolutionary Party.

National Action Party supporters have occupied City Hall in Monclova since Dec. 27.

The army barred the sale of liquor in Monclova on New Year's Eve to curb violence among crowds in the main plaza that reached 5,000 during the swearing-in ceremonies.

Also under army control was Piedras Negras, across the border from Eagle Pass, Texas. The municipal building and jail complex were burned during the weekend by members of the National Action Party after the Institutional Revolutionary Party's candidate was sworn in as mayor. At least one man was killed and 80 were injured.

In the towns of Escobedo and Nadadores, National Action supporters prevented Institutional Revolutionary Party candidates, the declared winners in the elections, from taking office and swore in their own candidates, a reporter for the newspaper Vanguardia said.

The mayor-elect of Escobedo, a state government representative and another man were grabbed, stripped to their undershorts and held by National Action Party supporters while officials tried to negotiate their release.

Cortes Guerrero said federal police in Monclova had received a report that the men had been freed after being beaten. But he said their families reported Tuesday that they were still missing.

In Nadadores, the mayor-elect and the government representative who were at City Hall on Monday for the swearing-in fled when they heard protesters approaching, a National Action official, Rosendo Humberto Burciaga Saucedo, said.The protesters smashed windows and punctured the tires on the government representative's car, he said.