Portland police are increasing patrols after a spate of vehicle break-ins this week, mostly in the city’s Bayside neighborhood, that appear to be connected.

About three dozen cars have been broken into overnight or in the early morning hours from late Monday through early Wednesday. Some of the cars were parked on streets, others in parking lots. Most had their windows smashed.

Lt. James Sweatt, a spokesman for the Portland Police Department, said the break-ins follow the same pattern, which leads him to believe that the same person or persons is involved. He said officers will increase patrols in the area.

Five cars were broken into late Tuesday or early Wednesday in the park-and-ride lot on Marginal Way. At least two more cars parked farther down Marginal Way near the Miss Portland Diner also were targeted.

Some were still parked there Wednesday afternoon, glass strewn on the ground nearby.

Previously, 30 vehicles were hit Monday night or Tuesday morning in the area of Somerset Street and lower Preble and State streets.

Many of the cars were parked on the street, but at least seven were rental cars parked at the Enterprise Rent-A-Car on Marginal Way, according to an employee there.

A suspicious person was seen in the area of the break-ins early Wednesday morning, Sweatt said. He was described as a white man, 5 feet 6 inches or 5 feet 7 inches tall, wearing a dark jacket, a single-strap shoulder bag and possibly a ball cap. He was seen riding a 10-speed bicycle.

Sweatt said cash was taken from the cars, but in many cases other valuables were left behind, including credit cards and electronics. Blood was left on some of the cars, suggesting the thief or thieves may have injured themselves. Police have taken samples of the blood to be sent to the Maine State Police crime lab in Augusta to develop a DNA profile.

That profile will then be compared with profiles in the state’s database to seek a match that could help police solve the crimes. If there is no match, the profile will be stored in the database in case a match is established in the future.

Sweatt also said fingerprints would be taken.

The Enterprise employee said the company had turned over video footage to police that clearly shows a person in the lot after hours. Sweatt said detectives would evaluate that video and release footage if it was credible.

Ted Talbot, spokesman for the Maine Department of Transportation, which manages the park-and-ride lot, said there are no security cameras in the lot.

A 2014 Portland Press Herald analysis of calls for service from the Portland Police Department showed that the most common crimes in the city include burglaries of motor vehicles, as well as of commercial and residential properties. The West End saw a higher percentage of the 714 car burglaries in the 12 months ending in February 2014 than other neighborhoods.

Marshall Smith, a Southern Maine Community College student who lives in Bayside Village, a large apartment complex on Marginal Way, said he usually keeps his Jeep parked underneath the building, which is secure.

He said he had heard about the break-ins but isn’t too worried.

“It’s not like this is a common thing,” Smith said.

Anyone looking to provide information can do so anonymously:

Mobile phone users can text the keyword “GOTCHA” plus their message to 274637 (CRIMES).

Go to the Portland Police Department website: www.portland-police.com and click “Submit an Anonymous Crime Tip.”

Call the department’s Crime Tip line at 874-8584.

Staff Writer David Hench contributed to this report.