PYEONGTAEK, South Korea — More than 40 South Korean protesters who oppose Camp Humphreys’ expansion remained jailed in Pyeongtaek on Monday after violent clashes Saturday with pro-U.S. residents and local police, authorities said.

Police said 42 protesters were jailed for holding an unauthorized rally outside a local police station. Police said they were members of the Task Force To Oppose the Expansion of the U.S. Bases in Pyeongtaek.

Camp Humphreys in Pyeongtaek is scheduled to triple in size and become peninsula’s main U.S. military installation under an agreement between the U.S. and South Korea. The group is also against a proposed U.S.-South Korea free trade agreement.

The protesters spurned a police order to halt the rally and then resisted when officers sought to disperse them, according to the Gyeonggi Provincial Police Agency.

The incident came close on the heels of clash earlier Saturday in which 400 protesters rallied outside the Pyeongtaek train station, according to Yonhap.

A van containing several protesters drove toward the entrance of Daechu-ri, a village near Camp Humphreys, to check reports that a large group of pro-U.S. South Korean demonstrators was formed to block any anti-U.S. rally in the village, the Korean news agency reported.

Task force members, according to Yonhap, say that around 9 p.m. the van was met by 200 members of the Anjung-ri Merchants Association who allegedly blocked its path, pulled the occupants from the van and began beating them.

The task force was quoted as saying three members of its group were attacked, and that one man remained hospitalized for treatment of cuts and fractures, including a head injury.

Kim Ki-ho, president of the Anjung-ri Merchants Association, said Monday that at least two association members were injured in Saturday’s clash with the protesters and were hospitalized.

He said he could provide no further immediate details on Saturday’s violence.

Hwang Hae-rym contributed to this report.