(CNN) -- Baby bottlenose dolphins are washing up dead in record numbers on the shores of Alabama and Mississippi, alarming scientists and a federal agency charged with monitoring the health of the Gulf of Mexico.
Moby Solangi, the executive director of the Institute for Marine Mammal Studies (IMMS) in Gulfport, Mississippi, said Thursday he's never seen such high death numbers.
"I've worked with marine mammals for 30 years, and this is the first time we've seen such a high number of calves," he said. "It's alarming."
At least 24 baby dolphins have washed up on the shores of the two states since the beginning of the year -- more than ten times the normal rate. Also, six older dolphins died.
In January 2009 and 2010, no calf strandings were reported, compared to four in January 2011, the institute said. During the month of February for those years, only one calf stranding was reported each year.
Blair Mase, lead marine mammal stranding coordinator for the National Oceanic and Atmospheric Administration (NOAA), echoed Solangi's concern.
"It's not common for this time of year to recover such young animals. When you put the numbers together, it's quite high compared to previous years."
The occurrence has prompted NOAA to designate these deaths as an "unusual mortality event" -- defined as a stranding incident that is unexpected or involves a significant loss of any marine mammal population.
While bottlenose dolphins are actually the most-frequently found stranding animal, the season usually begins in March, according to Mase.
"We receive reports of stranding year round. We get an average of 700 total every year in the Southeast," she said.
While scientists have seen baby dolphins wash up in the past, "This is not during the months that they should be," said Solangi. "We keep getting reports of new ones all the time, and February isn't over yet."
There have been 13 unusual mortality events involving dolphin deaths in the Gulf of Mexico since 1991, Mase explained.
Marine mammals are particularly susceptible to harmful algal blooms, infectious diseases, temperature and environmental changes, and human impact, she said.
"Unfortunately we don't have a smoking gun here. We're looking at the possibility of an algal bloom but we don't see any evidence of a bloom going on in the water. Temperatures are a bit cooler, so we're looking into water temperature data and seeing if that has a role, but it's a little bit too early to tell."
The IMMS said it has been able to perform full necropsies on a third of the 24 calves. The majority of the calves were too decomposed for a full examination, but the institute has taken tissue samples for analysis.
The institute does not have conclusive results on the causes of death.
Following the Deepwater Horizon rig explosion last April, which killed 11 workers and caused the worst oil spill in U.S. history, there has been heightened concern over the environmental impact.
Due to the government's ongoing litigation with BP, which owned the oil well that erupted into the Gulf of Mexico, NOAA said it must operate under specific protocol in handling the dead dolphins. That might mean a delay in seeing the necropsy results.
"In a world when we wouldn't be dealing with oil-spill protocols, we'd typically get results in about three weeks to a month," Mase said. "We aren't going to see results as quickly as we'd like to. We will be making sure these samples are collected, taken back and analyzed, but it could take several months."
While none of the 30 dolphins were found with any oil on them, Mase said the agency is not ruling anything in or out on the cause of death.
"Frankly, it's just too early to tell at this point. It's obviously on everyone's radar screen. Everyone's concerned about any impact of the BP oil spill, but we have to be very cautious as to identify any particular cause. We won't know until we have these samples analyzed and be able to identify the source."
The most worrisome concern is that dolphin stranding season has yet to officially begin, according to Solangi.
"Whatever it is, I hope it is just an anomaly. It certainly has connotations on reproduction and the population," he said.
"Unfortunately, I think this is not the end of what we will be seeing."
By Vivian Kuo, CNN