April 3 (Reuters) - The U.S. National Highway Traffic

Safety Administration (NHTSA) said on Thursday it has closed its

probe into 258 Zoox vehicles over a braking issue, after the

Amazon ( AMZN ) self-driving car unit recalled them and updated

their software.

The transport agency had opened the probe in May following

two rear-end collisions that injured motorcyclists after the

automated vehicles braked unexpectedly.

In March, Zoox agreed to recall 258 vehicles and said it

addressed the braking issue by updating their software that made

the vehicles brake unexpectedly when bicyclists or motorcyclists

were near or approaching rapidly.

The probe was closed after NHTSA's Office of Defects

Investigation analyzed Zoox's data demonstrating the resolution,

the agency said.