ATHENS (Reuters) - Sarah Mardini, one of two Syrian sisters who saved over a dozen refugees in 2015 by pulling their sinking dinghy to Greece, has been arrested for alleged people smuggling, her lawyer said on Friday.

FILE PHOTO: Refugees and migrants arrive on a raft on the Greek island of Lesbos, November 9, 2015. REUTERS/Alkis Konstantinidis/File Photo

Greek police said on Tuesday they had arrested two members of an aid organization on the island of Lesbos and were investigating a total of 30 on suspicion they smuggled migrants into Greece, spied and laundered money.

Mardini, 23, who is being held in a maximum security prison in Athens, has denied all charges, her lawyer Haris Petsikos told Reuters.

“She was strictly doing volunteer work. There is not a piece of evidence against her,” he said.

The other person arrested is German national Sean Binder, 24, a volunteer who has lived most of his life in Ireland. He is also represented by Petsikos and also denies the charges.

Authorities said the suspected crime gang allegedly “provided direct assistance to organized migrant trafficking rings”.

They are accused of establishing and joining a criminal organization, money laundering, espionage, violating state secrets, counterfeiting and offences against the immigration code and electronic communication legislation.

Mardini, who settled in Germany and split her time between there and Greece, was not in Greece when some of the alleged crimes were committed, Petsikos said.

A date for a trial has not yet been set. Under Greek law, Mardini could be held for up to 18 months.

Sarah Mardini and her younger sister Yusra, a UNHCR goodwill ambassador and swimmer who competed in the 2016 Rio Olympics with the first ever refugee team, fled Damascus in 2015 for Turkey.

They boarded an overcrowded dinghy to Greece and, when it began taking on water, jumped into the sea and dragged it for hours to Lesbos, saving the lives of 19 others.

Nearly a million Syrians, Afghans and Iraqis crossed to Lesbos from Turkey in 2015, at the height of Europe’s refugee crisis, before traveling onwards to northern Europe. Dozens of aid groups operated on Lesbos at the time.

Hundreds of refugees and migrants have drowned trying to cross the narrow but dangerous stretch of water between Turkey and Greece.