State and local police found suspected explosives and illegal firearms in Marlborough and Framingham on Tuesday during an investigation that began when an armed man tried to rob a resident, authorities said.

According to the Middlesex district attorney’s office, Marlborough police responded at 3:30 a.m. Tuesday to a home on Boston Post Road in that city for a report of a man dressed in black with a firearm. The man had come to the victim’s home and demanded money, and then struck the victim in the face with a cellphone, authorities said.

Police arrested Andrew Josefek, 40, of Framingham, who had a firearm and two knives with him, authorities said. Officers then searched his vehicle, where Kelly Walker, 35, of Framingham, was inside and found seven explosive devices, as well as firearms, the office of District Attorney Marian T. Ryan said in a statement. State Police were called and determined that four of the devices were live.

Walker was also arrested and the pair was arraigned in Marlborough District Court.

Josefek pleaded not guilty to charges of possession of explosives, armed assault with intent to rob, assault and battery with a dangerous weapon, carrying a dangerous weapon, three counts of carrying a loaded firearm without a license, two counts of possession of a large capacity feeding device, three counts of possession of a firearm without a license, and conspiracy to violate the drug laws and conspiracy, Ryan’s office said.

Walker was charged with possession of explosives, armed assault with intent to rob, assault and battery with a dangerous weapon, possession of a firearm without a license, conspiracy to violate the drug laws, and conspiracy, according to Ryan’s office.

Both suspects were ordered held pending a dangerousness hearing Thursday.

At about 2:30 p.m. on Tuesday, the bomb squad and Marlborough and Framingham police searched Josefek’s home in Framingham and found additional firearms and explosive devices, the district attorney said. Those devices were rendered safe by the State Police Bomb Squad.

Olivia Quintana can be reached at olivia.quintana@ globe.com. Follow her on Twitter @oliviasquintana.