A match-fixing scheme involving players and clubs in Spain's lower divisions has been dismantled by police, La Liga has announced.
More than 20 people were detained across Spain as part of an operation launched by police, in conjunction with Europol, on Monday.
The matches in question took place in the third and fourth divisions both last season and this, and the fixing scheme reportedly involved Chinese betting sites.
Marca reported that 51 games are potentially troublesome: 10 from 2015-16, 26 from 2016-17 and 15 from the first half of 2017-18. Most involve semi-professional clubs from the third and fourth tiers of the Spanish football pyramid, and although Castilla's 2-0 win at Cerceda in November 2017 is being looked at, there is no suggestion that anybody at Madrid is under investigation.
A La Liga statement said: "La Liga wants to manifest the extraordinary work done by the national police regarding the complex dismantling of an organised group dedicated to criminal activity focused on obtaining financial gain by predetermining results in soccer games in the country.
"This police operation demonstrates that the systems for the protection of integrity created by La Liga, in order to protect the cleanliness of all Spanish football competitions, have been crucial in the detection and reporting the games alleged to have been tampered."
Last year, the general director of anti-fixing organisation Federbet warned that fixing was widespread in Spain's lower divisions, with much of the betting on games taking place in Asia.
In April last year, Spanish police arrested several people, including players and the coach of third-tier side Eldense, following the club's 12-0 defeat at Barcelona B.
ESPN FC's Madrid correspondent Dermot Corrigan contributed to this report