BARCELONA, Spain (AP) — Authorities on the European island nation of Malta have contested accusations made by a group of nongovernmental organizations a day earlier regarding a migrant boat in distress.

“Following multiple verifications of reported position through multiple searches, no boat was sighted in the reported position,” the Armed Forces of Malta said in an email to The Associated Press on Tuesday.

On Monday, four rescue groups operating in the central Mediterranean accused Maltese authorities of coordinating the return of around 500 people to eastern Libya where they were subsequently imprisoned, in violation of international maritime law.

The group of migrants, including 55 children and pregnant women, had been trying to reach Europe on May 23 aboard a rusty iron fishing vessel when they reported to Alarm Phone — a hotline for migrants in distress — that they were adrift and taking in water, according to the NGO.

Communicating by satellite phone, the migrants shared their GPS location with Alarm Phone multiple times, showing they were in international waters inside Malta’s area of search and rescue responsibility.

Alarm Phone say they relayed their position and distress to Maltese authorities repeatedly, but received no confirmation that a rescue operation had been launched. Humanitarian rescue ships and plane also searched for the vessel in vain. Alarm Phone lost contact with the migrants on the morning of May 24.

Two days later, Alarm Phone says relatives of the migrants reported they had been returned to Benghazi, Libya, and imprisoned.

The International Organization for Migration and the U.N. Refugee Agency told The Associated Press that 485 people were brought back to Benghazi by a vessel belonging to the self-styled Libyan National Army, a force in the east of the country led by military commander Khalifa Hifter.

IOM spokesperson Safa Msehli said that the migrants were taken to the Qanfouda detention center, but couldn't confirm that it was the same group of people reported by Alarm Phone.

Both U.N. agencies have repeatedly condemned the return of migrants and refugees to Libya, saying the lawless nation shouldn't be considered a safe place for disembarkation as required by international maritime law.

In their emailed statement, Maltese authorities added that they “have no jurisdiction over any autonomous actions conducted in international waters.”

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