HOUSTON (AP) — The deaths of more than 120 dolphins off the Texas coast has prompted a federal agency to declare the event “unusual” and launch an investigation into whether they were related to a drought-related algae bloom or a more widespread mortality event that has plagued the northern Gulf of Mexico for two years.

The U.S. National Oceanic and Atmospheric Administration has called the stranding of 123 dolphins on Texas shores from November through March an “unusual mortality event,” an official federal listing that allows the agency to access additional funds and set up a team of researchers.