MD Anderson’s Houston-based primary hospital, one of the top cancer centers in the US, has flooded because of torrential rains from tropical storm Harvey — leaving cancer patients unable to receive scheduled treatment through Friday.

The cancer hospital’s main building, as well as several MD Anderson satellites around Houston, will stay closed for appointments, but the hospital staff is “identifying those patients with the most urgent medical or treatment needs and directly contacting them,” according to a statement by Karen Lu, MD Anderson’s senior vice president and chief medical officer.

Photos on Twitter show the streets surrounding the medical center completely flooded, keeping some hospital personnel from returning to work. Murky waters can also be seen in the center’s garage and lobby. The hospital, however, hasn’t been evacuated, STAT reports, and in-hospital patients are continuing to receive treatment. MD Anderson has a so-called ride-out team of doctors and nurses who can provide care after storms hit.

In 2001, the hospital was flooded during Tropical Storm Allison, and later was upgraded with floodgates and submarine doors to stave off future flooding. Mechanical and electrical life-saving equipment was also relocated for protection.

As the floodwaters recede, the hospital should open its doors to outdoor patients again. In the meantime, medical staff is contacting patients to reschedule appointments that have been cancelled, Lu’s statement says.

Update August 30th 02:05PM ET: The story has been updated to include Karen Lu’s statement.