Susan Boyle's emotional outburst at roadside service station

Scottish star Susan Boyle sparked concern after she reportedly began screaming and weeping at a service station on Thursday.

The singer had ordered a cup of coffee at a roadside rest stop in Cheshire when she became upset and allegedly began shouting and cursing at staff.

When a fellow customer tried to calm Boyle down, she is said to have put her head in her hands and cried.

A pal tells The Sun that Boyle was feeling exhausted after appearing in her I Dreamed A Dream stage show in Manchester.

The source explains, "She wanted to go home as she was tired and upset. Susan is very sorry to anyone she upset."

Boyle, who will be performing in the musical until October has had a string of publicised meltdowns - most notably, she checked into The Priory rehab clinic to be treated for exhaustion after coming in second place on Britain's Got Talent in 2009.