CONWAY, N.H. – The FBI has joined the investigation into the disappearance of a 20-year-old Portland woman whose car was found in a parking lot, still running with her toddler in the back seat.

Three agents from the bureau’s New Hampshire office started working on the disappearance of Krista Dittmeyer on Tuesday afternoon, said Conway Police Lt. Chris Perley. The investigation had been conducted by Conway police and New Hampshire state police.

A passer-by discovered Dittmeyer’s Nissan Sentra in the parking lot of the Cranmore Mountain Resort in North Conway around 6:30 a.m. Saturday. The engine was running, the flashers were on, a door was open and Dittmeyer’s 14-month-old daughter was inside.

Police have said there’s nothing to indicate that Dittmeyer, a single mother who works as a waitress in South Portland, left her car or her daughter voluntarily.

The case has made headlines nationally. Dittmeyer’s disappearance has been featured on television shows such as “Nancy Grace” on CNN and on the website of “America’s Most Wanted.”

Police continued to analyze evidence Tuesday. They had searched Dittmeyer’s car and another vehicle. Perley declined to describe the search further.

Dittmeyer’s cellphone records were also being scrutinized.

Perley declined to elaborate on a report that blood was found in Dittmeyer’s car, citing his department’s policy not to comment on specific pieces of the investigation.

The Union Leader of Manchester, N.H., attributed the information to Carroll County Sheriff Christopher Conley, who said Tuesday that he was referring all media questions to Conway police in the interest of the continuity of the case.

The sheriff’s office is not part of the investigation, Perley said, but a deputy was involved in the search for Dittmeyer on Saturday.

Perley said the father of Dittmeyer’s daughter is not a suspect because he was not in the area at the time she disappeared.

Dittmeyer’s supporters have been putting up “missing” posters around Conway, Portland and Bridgton. They plan a candlelight vigil for Dittmeyer, a 2008 graduate of Lake Region High School, starting at 8 p.m. Thursday at Stevens Brook Elementary School in Bridgton.