FLAGSTAFF, Ariz. (AP) — The Latest on a Feb. 10 helicopter crash at the Grand Canyon (all times local):

5:30 p.m.

A medical examiner's office says newlyweds who were pulled from a helicopter crash at the Grand Canyon died of complications from burn injuries.

The Clark County coroner's office released the causes of death Tuesday for 29-year-old Ellie Milward Udall and 31-year-old Jonathan Udall. They were among six British tourists on a sightseeing tour Feb. 10 when their helicopter crashed.

Three died at the scene and the Udalls later died at a Las Vegas hospital. Another passenger and the pilot remain in critical condition.

Ellie Udall's family said in a statement that she never regained consciousness in the burn unit and asked for privacy.

The company that operated the helicopter said this week that it's adding fuel systems to its fleet that could prevent or lessen burn injuries.

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2:45 p.m.

The company whose helicopter was involved in a deadly crash at the Grand Canyon is adding crash-resistant fuel systems to its fleet.

Papillon Airways announced an agreement Monday with StandardAero for 40 fuel tanks that expand, rather than rupture, on impact. The new tanks also have self-sealing components.

The National Transportation Safety Board has urged the Federal Aviation Administration to require that all helicopters have the systems. Right now, they're required only for helicopters newly certified after 1994.

Papillon declined comment Tuesday on what led to its decision.

The system for the Airbus EC130 B4 that crashed and burned Feb. 10 wasn't standard but a retrofit became available last year.

Five British tourists died. At least one suffered thermal injuries.

The pilot and another passenger remained in critical condition Tuesday.