Complaints of a strong odor Monday inside a business park along Route 22 just north of Bethlehem caused 400 people to be evacuated and sent several dozen to area hospitals with complaints of nausea and vomiting. While emergency crews filled the parking lot at 90 S. Commerce Way with ambulances, firefighters combed through the building with hand-held air measuring units to try to track down the scent that caused a flurry of 911 calls, Northampton County dispatchers say. The building sits on 7.4 acres in Hanover Township, Northampton County, and as crews searched inside the building, evacuees outside complained of nausea and vomiting, with several sitting in a grassy area until paramedics could tend to them. The parking lot soon became a triage unit with different-colored tarps for potential victims to be laid out on. Officials said 31 people were taken to area hospitals for further evaluation, and UGI spokesman Joe Swope said 400 were evacuated from the building. But as of Monday evening, exactly what caused the odor remained a mystery, said Township Manager John Finnigan. "Everything has checked out so far," Finnigan said several hours after the call came in just before noon Monday. "There was no gas leak inside. There was no problem with the building's rooftop units. But it's been declared safe." An open investigation into the incident remains ongoing and federal crews were sent to serve as a resource to help local authorities, said Leni Fortson, spokeswoman with the Occupational Safety and Health Administration. A total of seven people were sent to Lehigh Valley Health Network facilities, said spokesperson Brian Downs. He said all those patients were considered stable and it was unknown if they were admitted or not. A dozen victims were taken to St. Luke's University Hospital in Fountain Hill and all were released, said spokeswoman Mariella Miller. She said seven other victims were taken to St. Luke's Anderson Campus in Bethlehem Township. Those victims remain stable, she said. Emergency crews checking gas lines found a small leak at a meter outside the building, but no measurable amounts inside, officials said. Swope also said the small gas leak outside the facility would not have caused a strong odor inside the building. That leak was repaired by Monday afternoon. By 3 p.m., crews declared the building was safe to enter and a large crowd of people gathered in an outside parking lot were allowed back in. The building houses five businesses, including a day-care center and offices for a travel agent and a mental health counselor, Finnigan said. The children inside the day-care center were taken by a bus to a nearby facility. The building's owner was advised to bring in an environmental service to try to determine what may have caused the odor. The owner was identified in court records as CO Summit Management and Realty Company in the 3400 block of Winchester Road in Allentown. The company did not immediately return a call asking for comment.