A German shipping company says four crew members from one of its vessels have been released a month after being kidnapped by pirates off Equatorial Guinea's coast.

Leonhardt and Blumberg says the container ship's crew members — including Ukrainian, Russian and Kiribati citizens — are in good spirits despite having spent 31 days in captivity.

German Federal Police said Saturday the Hansa Marburg's sailors were freed Thursday following intense negotiations and have now arrived in Germany.

The shipping company in a statement late Friday didn't specify whether a ransom was paid and said it won't comment on the circumstances of their release "in order to avoid encouraging further criminal acts of this kind."

The ship had been attacked 130 miles (210 kilometers) southwest of the West African port of Malabo.