A recent rape at a southwest Lawrence home may be related to multiple other rapes in the city that have occurred since 2004, police said Monday.

In all five cases, police said the attacker was armed with a weapon, sometimes a gun.

A 19-year-old Kansas University student was attacked by an unidentified male suspect who entered her home with a handgun about 2 a.m. Dec. 1, police said. The next day, more than a dozen Lawrence officers and detectives searched grassy areas along the Kansas Highway 10 bypass and the area of 27th Street and Wakarusa Drive in southwest Lawrence looking for evidence regarding the latest rape.

“We do have strong information to believe that this attack is related to the other four attacks in the city,” said police Sgt. Bill Cory. “We take these crimes very seriously.”

In what’s been called a major case investigation, Cory said detectives have devoted several thousand hours in investigating the cases involving a total of six sexual assault victims.

Police said last week’s rape is believed to be related to these cases:

— On July 14, 2004, an unidentified man entered a southwest Lawrence apartment and raped a Kansas University student, who was between 20 and 25 years old, who was sleeping.

— On Dec. 29, 2004, two women, ages 19 and 20, were raped inside an apartment at Highpointe Apartments, 2001 W. Sixth St.

— On June 13, 2006, an unidentified man entered a central Lawrence home and raped a 21-year-old woman.

— On March 22, 2008, an unidentified man entered an apartment at Lorimar Townhomes, 3801 Clinton Parkway, and sexually assaulted a 20-year-old KU student.

All of the attacks have occurred between about 2 a.m. and 4 a.m. and during periods when KU students are on some type of a break from school. Students returned from Thanksgiving break last Monday, the day of the most recent attack.

Police haven’t always said how the attacker gets into the homes. In at least one of the earlier cases, entry to the home was through an unlocked door.

After the March assault, police Capt. Dan Ward described the sexual attacks as “terrible” and said “they last awhile.”

The suspect is described as a white man between 25 and 40 years old, 5 feet 9 inches to 6 feet tall, with a slim build. The suspect was described as weighing 160 pounds.

Riley County Police said they were investigating several rapes and assaults in Manhattan, home to Kansas State University, and the cases could be related to the Lawrence cases. The crimes there date back to 2000, though the suspect’s description in the Riley County attacks isn’t completely similar to those of the Lawrence attacker.

Cory wouldn’t speak to the cases in Riley County.

Lawrence police said anyone with information about the sexual attacks is asked to call investigators at 830-7430 or Douglas County Crimestoppers at 843-8477 (TIPS), where information about crimes can be submitted anonymously.

“People need to be aware of their surroundings,” said Cory, who encouraged people to report any suspicious activity to police and to make sure their windows and doors are locked at night.

KU is also urging students to take safety precautions in the wake of the assaults, by being aware and alert.