Eight Navy members aboard the USS Abraham Lincoln have attempted suicide since the beginning of their extended deployment, a top Navy official said in a letter obtained by NBC News.

The length of the deployment, which some service members on board the carrier had described as extraordinarily tough, has raised concerns about supply shortages and the effect on sailors’ mental health.

No deaths have been attributed to suicide during the deployment.

The number of suicide attempts includes those by crewmembers and sailors from the carrier air wing, strike group and destroyer squadron staff; escorting destroyers; and all embarked aviation squadrons, according to the letter, which acting Navy Secretary Hung Cao sent to Sen. Kirsten Gillibrand, D-N.Y.

About 7,500 service members, primarily sailors, are part of the strike group.

A Navy official said the letter was delivered to Gillibrand on Tuesday.

The official said the number of sailors who jumped overboard while the Lincoln was in the Middle East providing operations for the war in Iran remains at two, as previously reported. The official did not provide details about the six other attempts.

In the letter, Cao answered a series of questions that Gillibrand, a member of the Armed Services Committee, had asked Defense Secretary Pete Hegseth in a previous letter.

The letter also addressed Gillibrand’s concerns about conditions and medical resources aboard the Lincoln.

In a statement, Gillibrand said the conditions on the ship were “serious and deteriorating.”

“Our troops and their families make immense sacrifices every single day, yet the president dismissed them with open disrespect,” she said.

President Donald Trump has previously said the deployment was “not nearly long enough.”

The ship was at sea without a port call for 286 days supporting the U.S. war with Iran. A typical deployment is six to seven months, with regular stops to replenish food supplies.

The Lincoln left San Diego in November. Its deployment was supposed to end in May, but it was extended after the war began in February. The ship stopped in Thailand this month and is now sailing back to San Diego after a stop in Guam.

Relatives of those on board raised concerns about food shortages and low morale and how the extended time at sea was “wreaking havoc” on sailors’ mental health, as one relative described it to NBC News last month.

Some military officials have played down or rejected those claims. In an op-ed in The Wall Street Journal last month, Adm. Brad Cooper, the commander of U.S. Central Command, described the concerns as “old news” that were resolved months ago.

This summer, a Navy official said that officials had not observed an increase in suicidal ideations or attempts aboard the ship and that service members’ well-being was a top priority.

“We take every service member’s well-being seriously and have religious, medical and mental health professionals available to assess and address concerns as they arise,” the official said in a statement.

The Lincoln has five chaplains, a clinical psychologist, a clinical social worker, behavioral health technicians and an embedded integrated prevention coordination counselor to support the crew, the Navy official said.

If you or someone you know is struggling or in emotional distress, call or text 988 or chat at 988lifeline.org 24/7 to reach the 988 Suicide & Crisis Lifeline. For additional resources, visit SpeakingOfSuicide.com/resources.