The U.S. Bureau of Prisons said Friday that Ana Belen Montes, one of the highest-ranking American officials ever found to have spied for Cuba, had been freed from jail early. She had been imprisoned for more than 20 years.

After being accused of exploiting her powerful position as a Defense Intelligence Agency (DIA) employee to leak material, including the identities of several U.S. spies, to Havana, Montes, 65, pled guilty to conspiracy to conduct espionage in 2002.

Aged 45, she was sentenced to 25 years in prison.

A U.S. citizen of Puerto Rican descent, Montes began working for the DIA in 1985 and rapidly climbed its ranks to become the agency’s top Cuba analyst.

Prosecutors said during this time Montes received coded messages from Havana over a short-wave radio as strings of numbers, which she would type onto a decryption-equipped laptop to translate to text.

She was accused of supplying the identity of four U.S. spies to Cuba, as well as other classified information.

Montes was arrested on Sept. 21, 2001, shortly before the United States invaded Afghanistan. Her lawyer, a leading espionage specialist, had argued she had cooperated without reservation.

At her sentencing a year later, Montes argued that she had obeyed her conscience and that U.S. policy to Cuba was cruel and unfair. “I felt morally obligated to help the island defend itself from our efforts to impose our values and our political system on it,” she said.

Ricardo Urbina, the sentencing judge, ruled she put fellow U.S. citizens and the “nation as a whole” at risk.

On her release from prison, Urbino had ordered Montes should be placed under supervision for five years, with her internet access monitored and a ban from working for governments and contacting foreign agents without permission.

Under President Joe Biden, the United States has eased some sanctions on Cuba but maintained its Cold War-era embargo on the island and stepped up restrictions on illegal migrants, arriving in record levels amid raging inflation and medicine shortages.