First responders search for survivors at the scene of an explosion at the Sina At'har health center in the north of the Iranian capital Tehran on June 30, 2020. (AMIR KHOLOUSI / ISNA / AFP)

Iranian authorities detained one person and were seeking at least four others over a deadly blast at a clinic in Tehran, the second major explosion to rattle the capital in less than a week.

The city’s attorney general, Ali Alghasi Mehr, said the people were wanted for their potential involvement in the blast late on Tuesday, and that a judicial investigation had been launched, according to the semi-official Iranian Students’ News Agency

The city’s attorney general, Ali Alghasi Mehr, said the people were wanted for their potential involvement in the blast late on Tuesday, and that a judicial investigation had been launched, according to the semi-official Iranian Students’ News Agency.

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In the immediate aftermath of the explosion, which killed at least 19 people in the busy Tajrish neighborhood, Tehran’s fire department blamed a leak in gas tanks on the building’s basement floor.

But on Wednesday, the head of Tehran City Council’s Health Commission, Zahra Sadr-Azam Nouri, said initial investigations indicated a fault in the electricity network connected to oxygen tanks kept in unsafe storage rooms was responsible. In comments carried by ISNA, Nouri said the fire department had repeatedly warned the clinic about safety measures but that it had never fully complied.

Mobile-phone video showed a large plume of smoke rising from the clinic as onlookers gathered. Twenty people escaped via windows and balconies.

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The clinic, which had 25 employees inside at the time of the blast, primarily carries out light surgeries and medical imaging. Last week, an explosion occurred close to a sensitive military site near Tehran which the defense ministry said was caused by a leaking tank at a gas storage facility. No deaths or injuries were reported.