A flock of birds dropped out of the sky in Mexico, with some of them dying as they collided with the concrete below. On February 7, swarms of yellow-headed blackbirds seemed to die, according to surveillance video that has gone viral due to the strange nature of the occurrence. Residents in Chihuahua, Mexico, phoned the police after noticing the dead birds on the pavement, according to local news site El Heraldo de Chihuahua, which broke the news first.

A safety camera captured footage of a swarm of birds falling on houses in a big black swirl. Though some of the blackbirds were able to fly away, others died. The birds may be seen in the footage lying motionless on the streets.

The video has received over 1.4 million views on Twitter and has been widely shared on Facebook. Local officials were unable to determine why the birds inexplicably dropped from the sky, but the viral footage sparked a slew of speculations.

According to USA Today, one veterinarian believes the birds were electrocuted while perching on electricity wires or ingested harmful gases from a heater. Some people on social media hypothesized that 5G may be to blame for the fatalities.

“This looks like a raptor-like a peregrine or hawk has been chasing a flock like they do with murmurating starlings, and they have crashed as the flock was forced low, you can see that they act like a wave at the beginning as if they are being flushed from above,” said Dr. Richard Broughton in an interview with The Guardian.