NORTON SHORES, Mich. (WZZM) -- One week ago Jessica Heeringa went to work and never came home. Now investigators are turning to DNA to assist in the search.

Friday, Norton Shores Police collected samples from Jessica's toothbrush and hairbrush; Jessica's parents also gave their DNA to investigators. Police say the DNA will help, in the worst case scenario, if a body was found.

Friday afternoon a Michigan State Police helicopter was spotted flying in the area of the Exxon gas station where police say Jessica was abducted, however authorities said it was part of routine air patrols over West Michigan and not related to any specific mission.

There is still no suspect or major lead in the case. Norton Shores Police Chief Daniel Shaw told WZZM 13 the man who had been questioned the past two days has been cleared in the case. He was one of 25 to 30 people they've interviewed this week.

Police are also testing samples of material found at the gas station where Jessica disappeared, but it's not clear what kind of substance it is.

"It could be transmission fluid, it could be break fluid, it could be anything, or it could be blood. If it is blood we want to know whose blood it is. Right now we're concerned if it's Jessica's blood, but right now we don't know what those samples were that were taken," said Shaw.

Police say they are by no means giving up, in fact, the investigative task force has committed to at least another week.