Their eyes wet with tears and their ears ringing from the wails and piped music of a ritual blessing, a group of women hastens up to the altar, each clasping banknotes worth two days' wages for many Mexicans.
"Who can give 200 pesos or more? Come up now," a young, slick-suited bishop purrs into a microphone, as pastors in ill-fitting dark suits with the menacing look of nightclub bouncers hold out a crimson velvet bag for the green notes worth roughly $18 (9.5 pounds).
"We want the best from God so we must give him the best. Come along, quickly," he says, in a strong Brazilian accent.
With Catholicism losing its lure for some, the Universal Church of the Kingdom of God (UCKG), a Brazil-based evangelical Christian group that promises miracles for cash, is spreading fast in Mexico, the second-biggest Catholic country after Brazil.
Its global annual income is now pegged at some $1 billion, raised by millions of followers in more than 50 countries from Angola to Venezuela, including the United States and Europe.
While it has survived probes in Brazil and sharp criticism elsewhere, Mexico is investigating whether the church adheres to its regulations for religious groups.
The church says it is being "persecuted like Jesus was." But critics claim it skilfully manipulates the poor.
"They are panic-mongers. They work on people's despair and their message is very effective in poor sectors," said Latin American religion specialist Elio Masferrer in Mexico City.
"It's an organization structured to make money. Its growth here has been meteoric."
MIRACLES
The UCKG is classed as part of the neo-Pentacostal or charismatic movement -- a rebirth of Pentecostal beliefs with strong emphasis on physical manifestations of the Holy Spirit in individuals such as speaking in tongues and working miracles.
Since taking root here around 1992 and winning a license to preach in 2001, the UCKG has expanded its winning formula to 48 temples in Mexico. Some seat several thousand.
On top of regular donations, preachers urge followers to put as much as 50,000 pesos in envelopes with requests for God to be taken to holy sites in the Middle East.
Whereas most religions collect coins for church upkeep, the UCKG tells people desperate to save a dying loved-one, find a job or restore a broken marriage that a large donation could move God to help them.
"My boyfriend ran off and married another woman. Ever since, I suffer. I cry, I can't sleep. I want God to bring me peace," said Monica Priorio, 29, who has attended daily UCKG services in a grimy Mexico City district for a year.
"I'm unemployed but if I find a job I'll give a lot. A good service makes you want to give everything you have."
Flashy services take place several times a day in converted theatres across Mexico. Some include exorcisms.
To crescendos of sugary piano music, the boyish preacher peppers his sermon with snappy prompts like: "Do you feel Jesus?" Some in the congregation wail and flail their arms.
Followers queue up for a healing blessing, in which pastors with contorted faces press on their heads and chant before flinging their hands away dramatically. As the music peaks some people weep, and the donation bags are brought out.
MONEY MACHINE
Founded in 1977 by Edir Macedo, the UCKG -- Igreja Universal do Reino de Deus in Portuguese -- soon reaped enough cash to buy a leading Brazilian television network, a bank, newspapers and radio stations.
"It has the marketing strategy of a big multinational," said Paris-based anthropologist and UCKG expert Marion Aubree.
"The problem is people give (money) freely. This church has used the miracle fairy tale like no other," said Aubree.
The UCKG denies misconduct, and followers say it brings them hope.
Its publications are packed with tales like the one of a penniless family that sent money to God and soon found itself in a luxury villa with a fleet of new cars.
"If your objective is high then so too must be the price of the sacrifice you pay," an editorial reads.
In mainly Catholic Mexico, evangelicalism has lifted the number of Protestants to 12 percent from 10 percent in 2000.
Macedo, a multi-millionaire, was probed for tax fraud in 1992 and linked to illegal drugs money. In 1995 a video showed him teaching pastors how to raise cash, pulling faces as he counted donations and saying the stingy could "go to hell."
More recently the church was probed in Britain over its money flows and placed on a blacklist in France.
"Most evangelical pastors are decent, respectable people, but this church is about making money," said Masferrer.
Some ex-members have tried to sue the church but hit a wall as collecting voluntary donations is not illegal.
Inside the Mexico City church, a sparkling white sanctuary from the filthy streets outside, pastors seek to convince first-timers. One, called Carmen, told Reuters her terminal lung cancer vanished days after she made a large donation.
"I went for a test and the doctor said: 'why are you here? there's nothing wrong with you.' God can move mountains."