PORTLAND — The American Red Cross is looking for type O negative blood donors to restore its inventory.

Donors of all blood types are needed during the summer, but the supply for type O negative blood has fallen to critically low levels, according to the American Red Cross. The demand for type O negative blood is always high because it can be transfused to patients with any blood type, especially during emergencies.

Shortages often occur during the summer. Fewer people are giving blood and schools hold fewer blood drives as summer vacation nears.

The American Red Cross is reaching out to eligible blood donors, sponsors and community leaders to recruit type O negative blood.

Eligible blood donors are asked to call 1-800-RED CROSS to locate a blood drive and make an appointment.