DHS agents arrest co-pilot on Delta Air Lines flight after landing in San Francisco

Department of Homeland Security agents arrested a co-pilot on a Delta Air Lines flight this weekend after the plane landed in San Francisco.

The unnamed pilot was put in handcuffs shortly after his flight from Minneapolis to San Francisco International Airport landed at about 9:35 p.m. on Saturday. Plainclothes arrested him in the plane and led him off the flight, the Daily Mail reported.

Passengers said that the group of 10 officers included agents from Homeland Security Investigations and others who were identified as federal air marshals.

"A group of people with badges, guns and different agency vests/markings were pushing their way through the aisle to the cockpit," a first-class passenger said.

She added that the officers "stormed the cockpit, cuffed the pilot, arrested him, walked him down the aisle and ushered him off the plane through the cabin doors located between first and coach."

Shortly after, a second team of agents entered the plane to collect the unidentified co-pilot's personal belongings.

While authorities did not immediately reveal why the co-pilot was apprehended, a senior federal official told Fox News that the co-pilot was taken into custody by Homeland Security Investigations on allegations involving child sexual abuse materials. 

The pilot who was left said he did not know what was happening.

A passenger asked a flight crew member, "'What's going on?' He said, 'I have no idea.'"

"And he genuinely looked like this was a surprise, that all of a sudden there was people on the plane, because he had us stand up, we were starting to take our stuff out for arrival and everybody was already in the overhead bin," the passenger said.