Danish police have launched an international search for a 64-year-old civil servant who they believe has left the country after taking more than 110m kroner (£15m) of public money meant for social services.

The unnamed woman, described as a trusted and longstanding welfare agency official, siphoned off the money over a 16-year period starting in 2002, DR radio reported.

The social affairs minister, Mai Mercado, said: “I am deeply shocked that there has apparently been a scam involving money that should have gone to underprivileged groups. This kind of thing is completely unheard of.”

Two internal investigations have been launched into how the embezzlement, which was first discovered in early September, could have happened and “how control systems could have failed to such an unprecedented degree over such a long period of time”, Mercado added.

The ministry said the suspect had worked for the agency for 40 years before being fired on 26 September, and had acquired “superuser” status, giving her high-level access to computer systems. A total of 274 payments were made to a private bank account between 2002 and this year.

The woman reportedly registered a company in 2006, which she wound up in 2016, and had filed for bankruptcy. Police did not exclude the possibility that others were involved in the fraud or the sum stolen could increase.

The state prosecutor for serious financial crimes, Morten Niels Jakobsen, told Politiken newspaper: “The suspect is currently abroad. We are in close contact with our international partners, so she will hopefully be arrested and handed over soon. It is also very important as much of the money as possible is returned.”

Jakobsen said investigators already had “a fairly complete picture” of how the fraud had been perpetrated. The woman, who lives in Copenhagen, had “used a highly disciplined and very systematic approach”, he added.

Welfare organisations that receive funding from the agency expressed outrage. “We have repeatedly had to discontinue projects when their funding runs out,” said Sabine Elm Klinker of the national association against eating disorders and self-harm.

“We’ve said goodbye to employees, stopped offering the help people need. It’s particularly bad when you have to halt a project that is having a real impact.”