Lawrence police officers are searching for four men, described in their early 20s, last seen in a white minivan after a reported aggravated robbery early this morning.A 25-year-old man told officers that four to five men hit him and kicked him while he was on the ground. The man said he had been with several people during the evening and given them $20 to buy “refreshments,” according to a police report.When they did not purchase the refreshments, the man said he asked them to return the money, which caused a verbal altercation that became physical. He said he was also missing $17.Officers were dispatched at 2:20 a.m. to an area in the 600 block of Florida Street. They found the reported victim walking west in the 1900 block of West Sixth Street.Hate crime reportedIn a separate incident Sunday, officers arrested a 25-year-old white Lawrence man on charges of battery and obstruction, and investigators are looking into the case as a possible hate crime, according to a police report this morning.Police responded to Lawrence Community Shelter and Drop-In Center, 214 W. 10th St., at 2:30 p.m. Sunday after a 54-year-old man said he was sitting inside reading a newspaper when the man walked behind him and began hitting him in the back of the head.A witness said he saw the suspect strike the victim in the face and on the head, according to the report. Police spokeswoman Kim Murphree said officers are looking into a hate crime characterization based on race or ethnicity.