Criminal investigators from the Food and Drug Administration are at the Massachusetts company whose steroid medication has been linked to a deadly meningitis outbreak.

A spokesman for the New England Compounding Center confirms that investigators were at the Framingham company Tuesday but he had no further comment.

FDA spokesman Steven Immergut said the visit is part of the investigation into the outbreak, which has killed at least 15 people and sickened more than 200 others in 15 states. Nearly all the victims had received steroid injections for back pain.

Federal and state investigators have said they have found fungus in more than 50 vials from the company, but they have not said whether they have pinpointed the source of the contamination.