Romania's Fed Cup captain, the former world number one and Grand Slam champion Ilie Nastase, has been heard making a derogatory comment about Serena Williams' unborn child.
As Romanian player Simona Halep was answering a question in English about Williams' pregnancy at Friday's Fed Cup draw in Constanta, the 70-year-old turned to one of his other team members and added in Romanian: "Let's see what colour it has. Chocolate with milk?"
A spokesman for the International Tennis Federation has told the BBC it is aware of the comments and has begun an immediate investigation.
"The ITF does not tolerate discriminatory and offensive language and behaviour of any kind," the statement reads.
"We are aware of alleged comments made by Romanian captain Ilie Nastase and have begun an immediate investigation so that we have the full facts of the situation before taking further and appropriate action."
Romanian journalists present did not ask anything more about the statement but appeared to try to pass off the comment as a joke.
This is the second time in a month that Nastase has made comments about the American world number two.
In late March he made unsubstantiated allegations about Williams' doping record to the Romanian website Digisport.
During the draw ceremony on Friday, Nastase also put his arm tightly around British team captain Anne Keothavong and asked for her room number, in earshot of the watching media.
I understand that Nastase made a similar comment to Keothavong, who is pregnant with her second child, at Thursday's team dinner.
George Cosac, president of the Romanian Tennis Federation, was at the draw but did not stay for the news conference and will not comment on the matter.
Great Britain and Romania begin their two-day World Group play-off tie on Saturday at 10:00 BST.
Williams is due to give birth in the autumn and had posted a picture on Snapchat on Wednesday, posing in a mirror with the message: "20 weeks", before deleting it.
But the news was confirmed later on Wednesday by her representative.
Williams will miss the rest of the season, having not played since the Australian Open, citing a knee injury.
Williams, who will return to world number one next week, would be eligible to retain her ranking under the WTA special ranking rule if she is ready to play her first tournament within 12 months of giving birth.
Best female player of the Open era
Williams announced her engagement to the co-founder of community news site Reddit, Alexis Ohanian, in December. The American is top of the all-time list of major winners since Grand Slams accepted professional players in 1968.
She is second only to Australian Margaret Court on the list of women's all-time Grand Slam singles titles leaders - Court won 24 titles between 1960 and 1973.
Court, who won the singles Grand Slam in 1970, gave birth to her first child in March 1972, aged 29, and returned to win three of the four Grand Slam events in 1973.
Williams is a five-time Tour finals winner, the last of which came in 2014, and was recently picked as the greatest female tennis player of the Open era by BBC Sport readers.