Authorities in the eastern Chinese province of Shandong have jailed three people for sending out tweets about an explosion at a chemical factory near their homes in Zibo city that wasn't reported by the country's tightly controlled media.



"Zibo police have sentenced two people surnamed Zhang to five days' administrative detention after arresting them and an individual surnamed Chen for spreading rumors," the Zibo city police department said in a statement. "The person named Chen is still under investigation."



"The police will crack down hard on anyone using the Internet to spread rumors," the statement said.



The three people are accused of sending out tweets saying that there had been a large explosion at the Zibo Dongda Chemical Industries after local residents heard a loud blast on evening.



"I heard it; it was very loud, and we didn't know [where it came from]," a Zibo resident surnamed Wang told RFA on . "Some people said here, others said there."



He said there had been no official explanation of the apparent blast.



"We still don't know where it came from," Wang said.



Toe the line

Online activist Li Fei said the sentences are likely linked to a renewed campaign to force members of the ruling Chinese Communist Party to toe the party line or face punishment under new disciplinary rules.



"Detaining netizens for so-called rumor-mongering is about freedom of expression," Li said on . "All this talk of so-called rumors and rumor-mongering is really about not allowing people to depart from the party line, online."



"They don't want to see any critical comment or debate from their citizens online," he said.



According to new regulations issued earlier this month, the party has banned any public or private comments that go against the official line approved by its leadership in Beijing.



The rules list eight moral and ethical principles that party members are expected to live by and target extravagant wining, dining and golf, as well as "improper sexual relations" with anyone, as well as the formation of party cliques, and factions that go against the leadership's political line.



According to former top party official Bao Tong, the rules show that the administration of President Xi Jinping is struggling to keep order within its own ranks.



"Not only is speaking out of line not a crime; it can be worthwhile," Bao wrote in a commentary on for RFA's Mandarin Service. "It's better than grand slogans, empty promises and spin, better than long live so-and-so and other main theme tunes."



"Speaking out of line is a good thing."

Repeated blasts

Bao said the ability to tolerate dissent is the sign of a healthy political system.



"If they have to suppress those who speak out of line wherever they find them, then that tells us they're at the top of a slippery slope, not that they're mighty or powerful," he wrote.



At least nine people were injured after a blast ripped through a chemical plant in Zibo on Aug. 24, amid a fire at the Shandong Runxing Chemical Technology Co, state media and residents reported at the time.



China has seen a string of lesser explosions since a massive explosion at a chemical warehouse ripped through the northern port city of Tianjin on Aug. 12, killing more than 160 people.



Tianjin was hit by a further warehouse blast on Oct. 12, just two months after the first, at a warehouse storing "alcohol materials" in Beichen district's Xiditou township, Xinhua news agency reported.



And residents of the eastern city of Hangzhou reported hearing a loud blast on Oct. 16 that was heard as far away as Ningbo, 160 kilometers away on the coast, residents told RFA at the time.



Reported by Yang Fan for RFA's Mandarin Service. Translated and written in English by Luisetta Mudie.