Two men were in Contra Costa county jails after their arrests by BART police responding to reports of violence, authorities said Monday.

At 12:41 p.m. Sunday, police at the El Cerrito Plaza station responded to a report of a man aboard a train threatening and challenging riders to a fight.

After the man, identified as Ronald Nalls, 37, of Oakland, initially refused to cooperate or leave the train, he was removed and handcuffed.

Nalls was booked into Martinez county jail on suspicion of obstruction of and battery against an officer, as well as for an Oakland police warrant for grand theft from a person. He was held Monday night on $20,000 bail, and $45,000 bail for the warrant, according to county records.

Just after 6 a.m. Monday, officers responded to the North Concord station for a report of a fight and arrested Charles Hemphill, 35, of San Francisco, on suspicion of disturbing the peace and violating a restraining order.

Hemphill was held Monday night on $5,000 bail, as well as $25,000 bail for an out-of-county warrant, according to county records.

Contact George Kelly at 408-859-5180.