Detectives are searching for both 50-year-old Matthew Branning of Sellersville and 47-year-old Michael Allen Stark of Royersford.
Both of the men work at Enchlor Inc., a manufacturing company in Silverdale.
At a news conference on Wednesday, Bucks County District Attorney Matthew Weintraub said Branning was last seen leaving work on Oct. 15.
Weintraub said surveillance video showed Branning pull up to an ATM in Sellersville around 4 p.m. that day. A person was partially visible in the back seat of his Lexus SUV, but investigators have not been able to determine who that person was.
Investigators tracked Branning's cellphone to Cape May, New Jersey where surveillance video shows Stark making a purchase at a Wawa at 9:24 p.m.
However, Branning is not seen in the video.
From there, investigators say toll information shows Branning's Lexus heading northbound, then westbound, on the Atlantic City Expressway.
Branning has not been seen or heard from since. His vehicle, the 2002 Lexus SUV with PA license plate KWS-5619, is also missing.
Stark, however, was spotted at a pawn shop in Garden City, Michigan on November 13.
Weintraub says investigators are concerned for Branning's well-being.
"It is out of his character to not contact family or for him to miss work," Weintraub said. "It is disturbing to me. I don't believe in coincidence, so candidly we expect foul play."
"We don't know that for a fact," Weintraub continued, "but it is definitely why we have such a heightened interest in this case."
There's also a bench warrant out for Stark's arrest for a separate case in Monroe County, Pennsylvania.
Anyone with information can contact Bucks County detectives at 215-348-6056, or submit tips anonymously through PA Crime Stoppers at 1-800-4PA-TIPS (8477) or through their website.