Greece last month reopened some passenger and freight rail routes that had been halted since a passenger and a cargo train carrying more than 350 people collided head-on on Feb. 28 on the same track near the city of Larissa, killing 57 people.

But no passenger trains had run on the Athens-Thessaloniki route where Greece’s deadliest crash on record occurred, as railway agency OSE and the route operator Hellenic Train needed more time to address safety issues raised by train drivers.

Workers at OSE and Hellenic Train “have surpassed their own limitations so that we were able to upgrade safety levels in extremely difficult conditions and ensure passengers feel safe,” Transport Minister George Gerapetritis said on Monday.

He said that Greek authorities were making a “huge effort” to complete a new signalling and remote control system across a 2,500-km (1,550-mile) rail network by September, in line with international safety standards.

A transport ministry official said issues such as secure mobile communications between drivers and signallers and lighting in tunnels have been addressed.

More rail services were expected to resume by next week, the official added.

The rail disaster sparked mass protests over safety shortcomings in an ailing network, the legacy of a decade-long financial crisis which ended in 2018.

The conservative government of Prime Minister Kyriakos Mitsotakis – who has called parliamentary elections for May 21, weeks before its term expires – has seen its lead over the leftist opposition narrow since the crash.

(Reporting by Angeliki Koutantou and Deborah Kyvrikosaios, editing by Mark Heinrich)