It was likely caused by the explosion of a gas cylinder used to store liquefied gas for medical purposes.
A massive fireball lit the sky above the Sina Athar Medical Center in the Iranian capital Tuesday evening after an unexplained explosion was reported at the site of a medical clinic building in northern Tehran's affluent Tajrish Square.
State-run IRNA news agency also quoted Mr Maleki as saying the dead included 15 women and four men.
Video posted online appeared to show more than one explosion and thick black smoke rising from the flames.
People in nearby Tajrish Bazaar rushed to the site, making a rescue operation hard, authorities said.
In a TV interview, Maleki said the explosion occurred as gas canisters caught fire in the clinic's basement.
Six people were injured, Saberian reportedly said.
No New Deaths But Holohan Says New Clusters Are Developing Here
Dr Holohan said: " We are starting to see a worrying trend, with the number of reported cases increasing and some new clusters ". Laois is also among a small number of counties that have had fewer than ten cases a week for the past eight weeks.
But a local newspaper announced on its social media Telegram channel that 17 people have been killed.
State TV reported there could be more blasts because there were a number of oxygen tanks remaining in the clinic.
Ambulances were deployed to the site while police blocked off all roads leading to it.
The clinic, which had 25 employees inside at the time of the blast, primarily carries out light surgeries and medical imaging, Harirchi said.
It took place in the Parchin area in the southeast of Tehran due to "leaking gas tanks", Iran's defense ministry said on Friday, adding there were no casualties.
Iran's capital Tehran was earlier hit with an explosion near a military complex.