Ex-police officer Dorner is accused of killing three people, including a police officer, last week, and a $1 million reward was posted for information leading to his capture.
Among reports that turned out to be false was one that resulted in the deployment of SWAT officers after someone said they saw Dorner at a Los Angeles home-improvement store, police said.
Investigators said that tip, on Sunday, may have been related to a couple arguing outside of the store, the Los Angeles Times reported.
The Los Angeles Police Department declared a tactical alert, meaning officers can be held over on their shifts and not respond to low-priority radio calls.
The manhunt for Dorner did not interfere with security arrangements for the Grammys award show Sunday, the fifth day police have been searching for the man accused of killing the daughter of a retired LAPD captain and her fiance and shooting three police officers, one fatally, in Riverside County.
On Sunday, Mayor Antonio Villaraigosa announced a $1 million reward.
"We will not tolerate anyone undermining the security of this community," Villaraigosa said at a news conference. "We will not tolerate this reign of terror."
Police Chief Charlie Beck said the reward was "the largest local reward ever offered to our knowledge."
The reason for such a significant reward, Beck said, was "not about capturing a fleeing suspect, but about preventing another crime, likely another murder."
Dorner is accused of carrying out the killings as part of a revenge campaign because of his 2008 dismissal from the LAPD for allegedly making a false accusation against his training officer. A day after the first two victims died, Dorner posted a manifesto online about his reasoning.
Officials said a search in a mountainous region about 100 miles east of Los Angeles was winding down, the Times said. That part of the search for Dorner began Thursday after his burning pickup was found on a forest road between two ski resorts.
On Saturday, Beck announced he was reopening the investigation into Dorner's firing, saying it wasn't "to appease a murderer" but to reassure the public the department is fair and transparent.