Two customers of fast-food chain McDonald's had unpleasant surprises this week when they found stray objects in their food orders.

Yesterday, Facebook user Espen Tian Bao ordered a Breakfast Deluxe meal from the chain's online service McDelivery.

When he received his meal, he found a piece of paper in his scrambled eggs.

His receipt showed that the order was fulfilled by the McDonald's branch at Safra Punggol.

McDonald's later replied to Espen's Facebook post, apologising for the incident and asking him to contact the company privately.

"We are concerned to hear about this because we strive to uphold the highest standards of food safety and hygiene," McDonald's added.

In a separate incident, a CK Ng Chung Keat posted a photo on McDonald's Facebook page on Wednesday, showing a half-eaten fish burger and a piece of plastic.

In his post, the Facebook user said he had bought the Filet-O-Fish at the fast-food chain's outlet at Tampines Mall on Wednesday morning.

He said he found the "piece of plastic embedded inside (the) fish patty" as he was eating it.

In his post, he also urged McDonald's to "work on the quality and hygiene checks of (its) products".

In response to queries from The Straits Times, a McDonald's spokesman said it is aware of the incidents and has been in touch with the affected customers.

"Upon being alerted, we took immediate action to send the foreign objects to our quality assurance team for further investigation," the spokesman said.

"We would like to assure all our customers that we are 100 per cent committed to serving safe and quality food at all times."

ST has contacted the National Environment Agency for more information.