(Reuters) -Shares of Singapore Telecommunications slid more than 2% on Monday after a technical failure at its unit Optus, Australia's No. 2 telecom carrier, disrupted emergency call services for 13 hours last week and has since been linked to four deaths.

The Singapore-listed stock fell 2.3% to S$4.31, its biggest single-day decline in nearly two months.

In a statement on Sunday, CEO Stephen Rue said the company's own initial investigation showed that established processes were not followed during a network upgrade on Thursday.

The technical failure potentially impacted 600 customers in the states of South Australia and Western Australia, and in the Northern Territory, according to the statement.

Last year, Optus was fined A$12 million ($7.91 million) by regulators for failing to provide emergency call services to thousands during a nationwide outage in 2023.

($1 = 1.5175 Australian dollars)