NEW YORK — The Boston Red Sox were banned from signing international amateur free agents for one year, a penalty assessed after Major League Baseball concluded the team broke rules on signing bonuses last summer.

MLB concluded the Red Sox and buscones – local trainer/representatives of the players – worked together to evade a $300,000 cap on signing bonuses to five Venezuelan prospects who were 16 at the time: right-hander Cesar Gonzalez, infielders Antonio Pinero and Eduardo Torrealba, and outfielders Albert Guaimaro and Simon Muzziotti.

A person familiar with the investigation said Friday the signing bonuses of those five were pooled with the bonuses of about 10 other players, and more than $300,000 was given to each of the five.

The person spoke on condition of anonymity because no public comments were authorized.

Boston may not sign international amateur free agents – players under age 23 residing outside the U.S., Canada and Puerto Rico – for the signing period that starts Saturday and runs through July 1, 2017. The contracts of the five players were voided, and they were declared free agents. They are allowed to keep their prior signing bonuses.

The investigation was first reported by Baseball America and details of the discipline were first reported by Yahoo.

Boston was subject to the $300,000 signing bonus limit in 2015-16 because it exceeded its $1,881,700 bonus pool in 2014-15, when the Red Sox agreed to a $31.5 million signing bonus for Cuban infielder Yoan Moncada.

The Red Sox took responsibility for breaking the rules, but are not sure who exactly in the Red Sox organization was aware at the time, the person familiar with the investigation said. The violations occurred before Dave Dombrowski was hired last August as president of baseball operations, taking over from general manager Ben Cherington.

“We are not at liberty to comment on an MLB investigation,” Red Sox spokesman Kevin Gregg said .

MLB is investigating whether Venezuelan law allows it to ban the buscones from representing the five players in the signing period that starts Saturday.