Real estate transactions involving Lotte Group founder Shin Kyuk-ho and the conglomerate's affiliates have come under the spotlight as prosecutors are looking into whether some deals were used as a way to create a slush fund for the owner's family, according to investigators and industry experts Tuesday. 

Lotte is South Korea's fifth-largest conglomerate, with the value of the real estate owned by its listed affiliates estimated at 10.7 trillion won ($9.12 billion) as of 2015, according to corporate tracker Chaebul.com. 

The value of the property owned by Lotte's eight affiliates is the nation's third largest following Hyundai Motor Group's 24.2 trillion won and the Samsung Group's 14.1 trillion won.

Considering most of Lotte's affiliates are not publicly traded companies, industry watchers cautiously say the total amount of its real estate assets, including property by unlisted companies, may surpass those by the nation's top two conglomerates.

Among the unlisted units are Hotel Lotte, which owns 8 trillion won worth of real estate across the nation, and Lotte Corp., which owns 75 percent of the land that Lotte World Tower is built on in southern Seoul. The initial public offering plan for Hotel Lotte was delayed for the foreseeable future amid the ongoing investigation.

Data by Chaebul.com also showed that Lotte subsidiaries have bought 11 pieces of land spanning 1.87 million square meters from Shin Kyuk-ho since 2000, with combined deals valued at 65.1 billion won.

Prosecutors have been looking into whether the 93-year-old tycoon sold his land to the group's affiliates at higher-than-market prices to create slush funds, also delving into other merger and acquisition deals between its affiliates.

Starting a confectionery in postwar Japan and expanding the business to his home country, Shin is known as "a genius of real estate investment" as he has bought land and greatly raised the value by building department stores, hotels and entertainment parks on them to turn them into glitzy retail strips.

As part of a widening investigation, the Seoul Central District Prosecutors' Office on Tuesday conducted a second round of raids into a total of 15 locations, including 10 of Lotte's affiliates.

Lotte Engineering & Construction Co. and Lotte Chemical Co. were included on the raid list.

Prosecutors previously raided the headquarters of the group and six of its affiliates, including Hotel Lotte Co., with some hundreds of investigative officials, on Friday. (Yonhap)