Houston hospitals have been forced to treat hundreds of COVID-19 patients in their emergency rooms — sometimes for several hours or multiple days — as they scramble to open additional intensive care beds for the wave of seriously ill people streaming through their doors, according to internal numbers shared with NBC News and ProPublica.

At the same time, the region’s 12 busiest hospitals are increasingly telling emergency responders that they cannot safely accept new patients, at a rate nearly three times that of a year ago, according to data reviewed by reporters.

The increase in ambulance diversions, coupled with the spike in patients being held indefinitely in emergency rooms, are the latest indicators that Houston hospitals are straining to keep up with a surge of new coronavirus patients. ProPublica and NBC News have previously reported that a public hospital in Houston ran out of a medication to treat COVID-19 patients and that a spike in at-home deaths from cardiac arrest suggests that the death toll from the coronavirus may be higher than official statistics show.