The phrase "were highly likely" is grammatically correct and can be used in written English.
It is typically used to express a strong probability or expectation about something in the past. Example: "They were highly likely to win the game, given their strong performance in previous matches."
We decided that both of these were highly likely.
Previous reports focused more on changes the scientists felt were "highly likely".
Experts said there were enormous pressures at work that were highly likely to make the sanctions disappear fairly quickly.
Supporters voiced confidence that the House and Senate were highly likely to approve the bill when Congress reconvenes early next month.
It came after the British Government urged all UK tourists to leave the country because further terrorist attacks were "highly likely".
The Centre for Reproductive Rights claimed in 2004 that 21 conservative states were highly likely to do so and nine somewhat likely.
About two-thirds of them were men - average age 63 - and they were highly likely to have had a family history of premature cardiovascular disease.
Although they are not legally binding, the fact that the proposals have such strong cross-party support suggested that they were highly likely to be adopted.
The comments come after the Foreign Office urged all tourists to leave Tunisia on Thursday as more attacks were "highly likely".
It found that governments often introduced laws much too late to prevent deaths and massive financial costs, but were highly likely to ignore scientific warnings and resist any regulation.
John Yates told the Guardian that details about his flights and airmiles, which formed the basis of a Mail on Sunday article in September 2010, were "highly likely" to have involved leaks from within the airline.
