Police and SWAT officers at the entrance of McLaughlin Eastshore State Park in Berkeley, July 19, 2016. (CBS)

BERKELEY (KCBS) — Police believe an armed suspect remains at large after a lengthy search of a park near the Berkeley Marina.

“We had two very legitimate witnesses who gave good descriptions,” Berkeley police Sgt. Andrew Frankel said. “That led me to believe they saw something.”

“It sounded to us like we were looking for someone potentially armed with a long gun,” Frankel said.

We're on scene with @BPDPIO and #EBRPPD after receiving calls about a man with a gun at Frontage and University pic.twitter.com/s6gfUf8Q25 — CHP Oakland (@CHPoakland) July 19, 2016

Berkeley police received several reports starting at 12:19 p.m. of a man on the pedestrian over-crossing near West Frontage Road carrying what appeared to be a rifle, Frankel said.

He was last seen walking into McLaughlin Eastshore State Park and was described as a white or Hispanic man in his 40s who was wearing a yellow shirt, Frankel said.

Frankel said California Highway Patrol officers, including a helicopter crew, and East Bay Regional Park District police were assisting to search for the man – and a day camp in the area was placed on lockdown.

Police cleared the scene and the park reopened around 6 p.m., according to Frankel, who believes the suspect remains at large.