US President Barack Obama has called for a federal investigation into the mining disaster in West Virginia that killed 29 people this month.
The deaths occurred after an explosion ripped through the Upper Big Branch mine, owned by Massey Energy, in Montcoal on 5 April.
Obama said the cause of the blast should be determined to prevent similar accidents from happening again.
Last week, the US Mine Safety and Health Administration released a report saying that while the mine’s operators had reacted to safety issues raised at the property, previous violations of safety standards were still a cause for concern.
The report shows there had been an increase in violations in 2009, with 515 citations last year and 124 so far for 2010.
Obama called for an inspection of all US mines with troubled safety records and stressed that the government has to ensure safety standards are maintained as a result of the findings.
The West Virginia disaster is the deadliest US mine accident to take place in the country in almost 40 years.